1. Field of the Invention
The present invention relates to an X-ray fluorescence spectrometer for analyzing the composition and the area density of a sample based on the FP method and a program used therein.
2. Description of the Prior Art
The X-ray fluorescence spectrometer has hitherto been well known, which utilizes the fundamental parameter method (hereinafter referred to as “FP method”) in analyzing the composition and the area density of a sample. According to the FP method, the theoretical intensity, based on the assumed concentrations of elements, the theoretical intensity of the secondary X-rays generated from elements contained in the sample is calculated and the assumed concentration of the element is successively approximately modified and calculated so that the theoretical intensity and the measured intensity measured with a detecting device can match with each other, thereby calculating the concentration of each of the elements contained in the sample. While elements such as oxygen and carbon, of which fluorescent X-rays is not measured, (i.e., the fluorescent X-rays of those elements may not be substantially measured because the intensity is low and because a considerable decay occurs as a result of absorption. Those elements are hereinafter referred to as “unmeasured elements”), are generally treated as residues, samples such as, for example, sludge, fly ash and biological specimen, which contain a large amount of unmeasured elements and of which atomic number cannot be specified, pose a problem. In this connection, there is a technique disclosed in the Japanese Patent Application No. 2004-251785.
According to this technique, as far as the unmeasured elements are concerned, the average atomic number is assumed and, using scattered X-rays as the corresponding secondary X-rays, the assumed average atomic number is successively approximately modified and calculated so that the theoretical intensity and the measured intensity can match with each other.
However, if the sample contains a unmeasured component (for example, CH2) consist of a plurality of unmeasured elements (for example, C and H), and if the unmeasured component is treated as a single element with assumption of the average atomic number, the mass absorption coefficient, elastic scattering cross section, inelastic scattering cross section and so on will represent a numerical value intermediate between numerical values of two light elements having the neighboring atomic numbers and will not, in most cases, represent an actual value. As a result, the concentration of the elements in the sample cannot be accurately calculated.
In an attempt to resolve the foregoing problems, the Japanese Patent Application No. 2004-251785 referred to above discloses that as far as the unmeasured elements other than hydrogen are concerned, the average atomic number is assumed and, using scattered X-rays as the corresponding secondary X-rays, and as far as hydrogen is concerned, the concentration of the hydrogen is assumed and, using different scattered X-rays as the corresponding secondary X-rays, and that the assumed average atomic number and the assumed concentration of the hydrogen are successively approximately modified and calculated so that the theoretical intensity and the measured intensity can match with each other. However, even with those measures, the previously discussed problems are still far from being resolved. Also, because of lack of measurement information, depending on the initial value of the assumed value, the concentration of the element contained in the sample tends to converge upon the value far from the value it should have been even though the theoretical intensity and the measured intensity match with each other, resulting in a different problem in that it cannot be calculated accurately.
In other words, with the technique disclosed in the Japanese Patent Application No. 2004-251785 referred to above, it may often occur that various samples which contain a substantial amount of unmeasured elements and whose atomic number cannot be specified are incapable of being sufficiently accurately analyzed.